Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$65.62	11.491%	$73.1604	$73.16	$73.15	$73.20
Purchase #2	$31.69	13.228%	$35.882	$35.88	$35.90	$35.90
Purchase #3	$77.79	11.722%	$86.9085	$86.91	$86.90	$86.90
Purchase #4	$31.56	7.393%	$33.8932	$33.89	$33.90	$33.90
Purchase #5	$120.81	5.406%	$127.341	$127.34	$127.35	$127.30
Purchase #6	$39.45	12.427%	$44.3525	$44.35	$44.35	$44.40
Purchase #7	$27.43	7.173%	$29.3976	$29.40	$29.40	$29.40
7 purchase totals =	$394.35		$430.9352	$430.93	$430.95	$431.00